Usually I've seen builds through to the end, but it's happened to me while trying to build a (much) smaller version of the Gekka that was supposed to be closer to the size of the actual knightmare frames. I couldn't find the right parts / sucked as a builder too much so I left it half-finished. So for my sake let's call it normal.

Speaking of the Gekka though, there was quite a long time in between when I built most of it and the arms. For a pretty long time, it was armless. Sometimes, you just need to step back and accept Rome wasn't built in a day (without going all Alarik on it).